The problem with something like lines=999 or columns=999 is that on some platforms (many Unix systems), the window is allowed to be arbitrarily large: it just won't fit on-screen and you won't be able to access it. In other words, it doesn't just assume that 999 means 'the largest size that will fit'.

On Windows, 999 makes the window as big as it can get, true, but it doesn't actually use the system maximize facility, forcing you to remember its previous size (the 'restore' size). A true maximize has the advantage that you don't need to remember the previous size: the operating system takes care of remembering the restoration point.

This points out the problems, but doesn't help outright, I realize. On Windows, the simalt mechanism seems to work for me. I use it to immediately maximize (true maximize) my GVim as soon as I start (I almost never work with an un-maximized window in most applications I use).

Yes, on Win XP, when Vim 7.2 is in utf-8 encoding, then Alt+Space does not work. In neither Esc mode nor writing mode one can access the window control menu (Maximize, Restore, Minimize, Move, Size and Close) of gvim with Alt+Space when in utf-8 encoding. My solution was to eliminate all Alt+__ bindings in _vimrc: